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	<LI><A HREF="#name">NAME</A></LI>
	<LI><A HREF="#synopsis">SYNOPSIS</A></LI>
	<LI><A HREF="#description">DESCRIPTION</A></LI>
	<LI><A HREF="#variables">VARIABLES</A></LI>
	<LI><A HREF="#usage">USAGE</A></LI>
	<LI><A HREF="#notes">NOTES</A></LI>
	<LI><A HREF="#requirements">REQUIREMENTS</A></LI>
	<LI><A HREF="#todo">TODO</A></LI>
	<LI><A HREF="#see also">SEE ALSO</A></LI>
	<LI><A HREF="#author">AUTHOR</A></LI>
	<LI><A HREF="#copyright">COPYRIGHT</A></LI>
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<P>
<H1><A NAME="name">NAME</A></H1>
<P>TapeChanger::MTX - use 'mtx' to manipulate a tape library</P>
<P>
<HR>
<H1><A NAME="synopsis">SYNOPSIS</A></H1>
<PRE>
  use TapeChanger::MTX;</PRE>
<PRE>
  my $loaded = TapeChanger::MTX-&gt;loadedtape;
  print &quot;Currently loaded: $loaded\n&quot; if ($loaded);</PRE>
<PRE>
  TapeChanger::MTX-&gt;loadtape('next');
  my $nowloaded = TapeChanger::MTX-&gt;loadedtape; 
  print &quot;Currently loaded: $nowloaded\n&quot; if ($nowloaded);
</PRE>
<PRE>

See below for more available functions.</PRE>
<P>
<HR>
<H1><A NAME="description">DESCRIPTION</A></H1>
<P>TapeChanger::MTX is a module to manipulate a tape library using the 'mtx' 
tape library program.  It is meant to work with a simple shell/perl script
to load and unload tapes as appropriate, and to provide a interface for
more complicated programs to do the same.  The below functions and
variables should do as good a job as explaining this as anything.</P>
<P>
<HR>
<H1><A NAME="variables">VARIABLES</A></H1>
<DL>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3AMT_%3Ditem_%24TapeCha">$TapeChanger::MTX::MT
=item $TapeChanger::MTX::MTX</A></STRONG><BR>
<DD>
What is the location of the 'mt' and 'mtx' binaries?  Can be set with
'$MT' and '$MTX' in ~/.mtxrc, or defaults to '/usr/sbin/mt' and
'/usr/local/sbin/mtx'.
<P></P>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3ADRIVE">$TapeChanger::MTX::DRIVE</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3ACONTROL">$TapeChanger::MTX::CONTROL</A></STRONG><BR>
<DD>
What are the names of the tape (DRIVE) and changer (CONTROL) device
nodes?  Can be set with $DRIVE or $CONTROL in ~/.mtxrc, or default to
'/dev/rmt/0' and '/dev/changer' respectively.
<P></P>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3AEJECT">$TapeChanger::MTX::EJECT</A></STRONG><BR>
<DD>
Does the tape drive have to eject the tape before the changer retrieves
it?  It's okay to say 'yes' if it's not necessary, in most cases.  Can be
set with $EJECT in ~/.mtxrc, or defaults to '1'.
<P></P>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3AREADY_TIME">$TapeChanger::MTX::READY_TIME</A></STRONG><BR>
<DD>
How long should we wait to see if the drive is ready, in seconds, after
mounting a volume?  Can be set with $READY_TIME in ~/.mtxrc, or defaults
to 60.
<P></P>
<DT><STRONG><A NAME="item_%24TapeChanger%3A%3AMTX%3A%3ADEBUG">$TapeChanger::MTX::DEBUG</A></STRONG><BR>
<DD>
Print debugging information?  Set to '0' for normal verbosity, '1' for
debugging information, or '-1' for 'quiet mode' (be as quiet as possible).
<P></P></DL>
<P>
<HR>
<H1><A NAME="usage">USAGE</A></H1>
<P>This module uses the following functions:</P>
<DL>
<DT><STRONG><A NAME="item_tape_cmd">tape_cmd ( COMMAND )</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_mt_cmd">mt_cmd ( COMMAND )</A></STRONG><BR>
<DD>
Runs 'mtx' and 'mt' as appropriate.  <CODE>COMMAND</CODE> is the command you're
trying to send to them.  Uses 'warn()' to print the commands to the screen
if $TapeChanger::MTX::DEBUG is set.
<P></P>
<DT><STRONG><A NAME="item_numdrives">numdrives ()</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_numslots">numslots ()</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_loadedtape">loadedtape ()</A></STRONG><BR>
<DD>
Returns the number of drives, number of slots, and currently loaded tape
values, respectively, by parsing <STRONG>tape_cmd('status')</STRONG>.
<P></P>
<DT><STRONG><A NAME="item_loadtape">loadtape ( SLOT [, DRIVE] )</A></STRONG><BR>
<DD>
Loads a tape into the tape changer, and waits until the drive is again
ready to be written to.  <CODE>SLOT</CODE> can be any of the following (with the
relevant function indicated):
<PRE>
  current       C&lt;loadedtape()&gt;
  prev          C&lt;loadprevtape()&gt;
  next          C&lt;loadnexttape()&gt;
  first         C&lt;loadfirsttape()&gt;
  last          C&lt;loadlasttape()&gt;
  0             C&lt;_ejectdrive()&gt;
  1..99         Loads the specified tape number, ejecting whatever is
                currently in the drive.</PRE>
<P><CODE>DRIVE</CODE> is the drive to load, and defaults to 0.  Returns 0 if
successful, an error string otherwise.</P>
<P></P>
<DT><STRONG><A NAME="item_loadnexttape">loadnexttape ()</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_loadprevtape">loadprevtape ()</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_loadfirsttape">loadfirsttape ()</A></STRONG><BR>
<DD>
<DT><STRONG><A NAME="item_loadlasttape">loadlasttape ()</A></STRONG><BR>
<DD>
Loads the next, previous, first, and last tapes in the changer
respectively.  Use <STRONG>tape_cmd('next')</STRONG>, <STRONG>tape_cmd('previous')</STRONG>, 
<STRONG>tape_cmd('first')</STRONG>, and <STRONG>tape_cmd('last')</STRONG>, respectively.
<P></P>
<DT><STRONG><A NAME="item_ejecttape">ejecttape ()</A></STRONG><BR>
<DD>
Ejects the tape, by first ejecting the tape from the drive
(<STRONG>mt_cmd(rewind)</STRONG> then <STRONG>mt_cmd(offline)</STRONG>) and then returning it to its
slot (<STRONG>tape_cmd(unload)</STRONG>).  Returns 1 if successful, 0 otherwise.
<P></P>
<DT><STRONG><A NAME="item_resetchanger">resetchanger ()</A></STRONG><BR>
<DD>
Resets the changer, ejecting the tape and loading the first one from the
changer.
<P></P>
<DT><STRONG><A NAME="item_checkdrive">checkdrive ()</A></STRONG><BR>
<DD>
Checks to see if the drive is ready or not, by waiting for up to 
$TapeChanger::MTX::READY_TIME seconds to see if it can get status
information using <STRONG>mt_cmd(status)</STRONG>.  Returns 1 if so, 0 otherwise.
<P></P>
<DT><STRONG><A NAME="item_reportstatus">reportstatus</A></STRONG><BR>
<DD>
Returns a string containing the loaded tape and the drive that it's
mounted on.
<P></P>
<DT><STRONG><A NAME="item_cannot_run">cannot_run ()</A></STRONG><BR>
<DD>
Does some quick checks to see if you're actually capable of using this
module, based on your user permissions.  Returns a list of problems if
there are any, 0 otherwise.
<P></P></DL>
<P>
<HR>
<H1><A NAME="notes">NOTES</A></H1>
<P>~/.mtxrc is automatically loaded when this module is used, if it exists,
using do().  This could cause security problems if you're trying to use
this with <CODE>setuid()</CODE> programs - so just don't do that.  If you want someone
to have permission to mess with the tape drive and/or changer, let them
have that permission directly.</P>
<P>
<HR>
<H1><A NAME="requirements">REQUIREMENTS</A></H1>
<P>Perl 5.6.0 or better, an installed 'mtx' binary, and a tape changer and
reader connected to the system.</P>
<P>
<HR>
<H1><A NAME="todo">TODO</A></H1>
<P>Support for Input/Export slots is not included, though it may be later.
Possibly works for multiple drives per changer, but I haven't tested it,
so I probably missed something.  'load previous' doesn't actually work,
because mtx doesn't support it (though the help says it does).</P>
<P>
<HR>
<H1><A NAME="see also">SEE ALSO</A></H1>
<P><STRONG>mtx</STRONG>, <STRONG>mt</STRONG>, <STRONG>tapechanger</STRONG>.  Inspired by <STRONG>stc-changer</STRONG>, which comes
with the AMANDA tape backup package (http://www.amanda.org), and MTX,
available at <A HREF="http://mtx.sourceforge.net.">http://mtx.sourceforge.net.</A></P>
<P>
<HR>
<H1><A NAME="author">AUTHOR</A></H1>
<P>Tim Skirvin &lt;<A HREF="mailto:tskirvin@uiuc.edu">tskirvin@uiuc.edu</A>&gt;</P>
<P>
<HR>
<H1><A NAME="copyright">COPYRIGHT</A></H1>
<P>Copyright 2001-2002 by the University of Illinois Board of Trustees and 
Tim Skirvin &lt;<A HREF="mailto:tskirvin@ks.uiuc.edu">tskirvin@ks.uiuc.edu</A>&gt;.</P>

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